ip page 31 - Dave's Blog

URI Fragment Info Roundup

Information about URI Fragments, the portion of URIs that follow the '#' at the end and that are used to navigate within a document, is scattered throughout various documents which I usually have to hunt down. Instead I'll link to them all here.

Definitions. Fragments are defined in the URI RFC which states that they're used to identify a secondary resource that is related to the primary resource identified by the URI as a subset of the primary, a view of the primary, or some other resource described by the primary. The interpretation of a fragment is based on the mime type of the primary resource. Tim Berners-Lee notes that determining fragment meaning from mime type is a problem because a single URI may contain a single fragment, however over HTTP a single URI can result in the same logical resource represented in different mime types. So there's one fragment but multiple mime types and so multiple interpretations of the one fragment. The URI RFC says that if an author has a single resource available in multiple mime types then the author must ensure that the various representations of a single resource must all resolve fragments to the same logical secondary resource. Depending on which mime types you're dealing with this is either not easy or not possible.

HTTP. In HTTP when URIs are used, the fragment is not included. The General Syntax section of the HTTP standard says it uses the definitions of 'URI-reference' (which includes the fragment), 'absoluteURI', and 'relativeURI' (which don't include the fragment) from the URI RFC. However, the 'URI-reference' term doesn't actually appear in the BNF for the protocol. Accordingly the headers like 'Request-URI', 'Content-Location', 'Location', and 'Referer' which include URIs are defined with 'absoluteURI' or 'relativeURI' and don't include the fragment. This is in keeping with the original fragment definition which says that the fragment is used as a view of the original resource and consequently only needed for resolution on the client. Additionally, the URI RFC explicitly notes that not including the fragment is a privacy feature such that page authors won't be able to stop clients from viewing whatever fragments the client chooses. This seems like an odd claim given that if the author wanted to selectively restrict access to portions of documents there are other options for them like breaking out the parts of a single resource to which the author wishes to restrict access into separate resources.

HTML. In HTML, the HTML mime type RFC defines HTML's fragment use which consists of fragments referring to elements with a corresponding 'id' attribute or one of a particular set of elements with a corresponding 'name' attribute. The HTML spec discusses fragment use additionally noting that the names and ids must be unique in the document and that they must consist of only US-ASCII characters. The ID and NAME attributes are further restricted in section 6 to only consist of alphanumerics, the hyphen, period, colon, and underscore. This is a subset of the characters allowed in the URI fragment so no encoding is discussed since technically its not needed. However, practically speaking, browsers like FireFox and Internet Explorer allow for names and ids containing characters outside of the defined set including characters that must be percent-encoded to appear in a URI fragment. The interpretation of percent-encoded characters in fragments for HTML documents is not consistent across browsers (or in some cases within the same browser) especially for the percent-encoded percent.

Text. Text/plain recently got a fragment definition that allows fragments to refer to particular lines or characters within a text document. The scheme no longer includes regular expressions, which disappointed me at first, but in retrospect is probably good idea for increasing the adoption of this fragment scheme and for avoiding the potential for ubiquitous DoS via regex. One of the authors also notes this on his blog. I look forward to the day when this scheme is widely implemented.

XML. XML has the XPointer framework to define its fragment structure as noted by the XML mime type definition. XPointer consists of a general scheme that contains subschemes that identify a subset of an XML document. Its too bad such a thing wasn't adopted for URI fragments in general to solve the problem of a single resource with multiple mime type representations. I wrote more about XPointer when I worked on hacking XPointer into IE.

SVG and MPEG. Through the Media Fragments Working Group I found a couple more fragment scheme definitions. SVG's fragment scheme is defined in the SVG documentation and looks similar to XML's. MPEG has one defined but I could only find it as an ISO document "Text of ISO/IEC FCD 21000-17 MPEG-12 FID" and not as an RFC which is a little disturbing.

AJAX. AJAX websites have used fragments as an escape hatch for two issues that I've seen. The first is getting a unique URL for versions of a page that are produced on the client by script. The fragment may be changed by script without forcing the page to reload. This goes outside the rules of the standards by using HTML fragments in a fashion not called out by the HTML spec. but it does seem to be inline with the spirit of the fragment in that it is a subview of the original resource and interpretted client side. The other hack-ier use of the fragment in AJAX is for cross domain communication. The basic idea is that different frames or windows may not communicate in normal fashions if they have different domains but they can view each other's URLs and accordingly can change their own fragments in order to send a message out to those who know where to look. IMO this is not inline with the spirit of the fragment but is rather a cool hack.

Warm Weekend

It was warm and lovely out this past Saturday and Sarah I and went to a new place for lunch, then to Kelsey Creek Park, and then out for Jane's birthday. We ate at Cafe Pirouette which serves crepes and is done up with French decorations reminding me of my parent's house. We got in for just the end of lunch and saw the second to last customers, a gaggle of older ladies leaving. I felt a little out of place with my "Longhorn [heart] RSS" t-shirt on. The food was good and in larger portions that I expected.

After that we went to Kelsey Creek Park and Farm. The park is hidden at the end of a quiet neighborhood, starts out with some tables and children's jungle gym equipment, then there's a farm which includes a petting zoo, followed by many little trails going off into the forrest. There weren't too many animals out and the ones we did see didn't seem to expect or want the sun and warm weather. We followed one of the trails for a bit and turned back before getting sun burned. You can see my weekend photos mapped out on Live Maps.

That night we went out with some friends for Jane's birthday. Eric was just back from the RSA conference and we met Jane and Eric and others at Palace Kitchen in Seattle located immediately adjascent to the monorail's route. The weather was still good so they left the large windows open through twilight and every so often you'd see the monorail pass by.

Zeno's Progress Bar - Stolen Thoughts

More of my thoughts have been stolen: In my previous job the customer wanted a progress bar displayed while information was copied off of proprietary hardware, during which the software didn't get any indication of progress until the copy was finished. I joked (mostly) that we could display a progress bar that continuously slows down and never quite reaches the end until we know we're done getting info from the hardware. The amount of progress would be a function of time where as time approaches infinity, progress approaches a value of at most 100 percent.

This is similar to Zeno's Paradox which says you can't cross a room because to do so first you must cross half the room, then you must cross half the remaining distance, then half the remaining again, and so on which means you must take an infinite number of steps. There's also an old joke inspired by Zeno's Paradox. The joke is the prototypical engineering vs sciences joke and is moderately humorous, but I think the fact that Wolfram has an interactive applet demonstrating the joke is funnier than the joke itself.

I recently found Lou Franco's blog post "Using Zeno's Paradox For Progress Bars" which covers the same concept as Zeno's Progress Bar but with real code. Apparently Lou wasn't making a joke and actually used this progress bar in an application. A progress bar that doesn't accurately represent progress seems dishonest. In cases like the Vista Defrag where the software can't make a reasonable guess about how long a process will take the software shouldn't display a progress bar.

Similarly a paper by Chris Harrison "Rethinking the Progress Bar" suggests that if a progress bar speeds up towards the end the user will perceive the operation as taking less time. The paper is interesting, but as in the previous case, I'd rather have progress accurately represented even if it means the user doesn't perceive the operation as being as fast.

Update: I should be clearer about Lou's post. He was actually making a practical and implementable suggestion as to how to handle the case of displaying progress when you have some idea of how long it will take but no indications of progress, whereas my suggestion is impractical and more of a joke concerning displaying progress with no indication of progress nor a general idea of how long it will take.

Search and Archive of Dave's Things

I now have search and an archive available for my site. I previously tried to setup crappy search by cheating using Yahoo Pipes and now instead I have a slightly less crappy search that works over all of the content that I've produced on my blog, uploaded to flickr or youtube, or added to delicious.

You can now read my first LiveJournal blog post or, for probably much more entertainment value, view all the photos and videos of Cadbury by searching for 'bunny'.

The search is only slightly less lame because although it searches over all my content, I still implemented it myself rather than getting a professional package. Also, the feed supports the same search and archive as my homepage so you can subscribe to a feed of Cadbury if you're so inclined and just skip all this other boring stuff. My homepage and feed implement the OpenSearch response elements and I've got an OpenSearch search provider (source) as well.

Dinner with Goodwins at Icon Grill

The Goodwin family, except for Michelle who is taking a class trip to Washington DC and New York, was in Seattle this week. Sarah and I met up with them for dinner last night at the Icon Grill. I enjoy the Icon Grill in general and last night was no exception especially having dinner with the Goodwins which was a lot of fun. It was particularly cold and at one point snowed. The Goodwin's are seeing all the classic tourist attractions in Seattle some of which are depicted in the following 1962 Seattle's Worlds Fair postcard. The postcard is featured on Paleo-Future and unsurprisingly the 1962 Worlds Fair favored Seattle's Space Needle and monorail.

Feed Folder Deprecated; Use Internet Explorer 8

Internet Explorer 8 has made my plugin Feed Folder obselete in functionality and implementation -- which is good!

I made Feed Folder for IE7 because I wanted the Live Bookmarking feature from FireFox. The Feed Folder plugin for IE7 would allow you to display your feeds as virtual folders in your Links Bar. When your feed is updated the virtual folder is updated as well with the new feed items. I use del.icio.us to store all my links so I could add virtual folders of my daily links, my friends blogs links, quick reference links, etc. etc.

My plugin relied on shell folders to implement the virtual folders I described above, but IE8 doesn't support shell folders in the Favorites Bar. But I'm OK with Feed Folder not working in IE8 since there's a much better implementation already there. IE8 does better than my plugin on a number of points: First, there isn't the horrible perf. issue that my plugin had on Vista. Second, when a feed is updated the virtual folder flashes to note the change in status. Third, unread items are bolded and the bolding bubbles up from feeds contained in subfolders. And lastly, the middle click button is supported to open items in a new tab.

Accordingly, I don't plan to work on Feed Folder anymore unless someone comes up with a good reason. Instead I mark Feed Folder deprecated and suggest you use Internet Explorer 8 instead.

To use this feature in IE8 simply drag a feed from your feed list in your Favorites Center onto your Favorites Bar. Or, when viewing a feed, click on the 'Add to Favorites' Star Plus icon thing in the upper left, and select 'Monitor on Favorites Bar'. A .url Internet Shortcut file is produced as usual, but if you open up the .url file you'll see there's some additional info about the feed.

Juanita Beach Visit and Map

Two weekends ago it was actually sunny and kind of warm so Sarah and I went down to Spud Fish and Chips and Juanita Beach Park. We ate fish and chips on the dock. I took a few pictures and this time actually put some geographical information on Flickr so now I've got a map of my tiny fish and chips journey. On the map click on the floating marks to view the associated photos.

Flickr provides access to the geo data associated with your photos via GeoRSS feeds. And Google Maps displays GeoRSS feed content on their maps allowing you even to edit the data but doesn't appear to let you easily export the GeoRSS. Live Maps does the inverse, allowing you to create and export GeoRSS data but not import it. I'd like both please. Oh well.

Internet Explorer 8 Beta 1 Released with Activities

Internet Explorer 8 Beta 1 is available now. I can finally talk about some of the stuff I've been working on for the past year or so: activities. Activities let you select a document, some text on a document, or a link to a document and run that selection through a web service. For example, you could select a word on a webpage and look it up in Wikipedia, select an address and map it on Yahoo Maps, select a webpage and translate it into English with Windows Live Translator, or select a link and add it to Digg.

IE8 comes installed with some activities based on Microsoft web services but there's a page you can go to to install other activities. However, that page is missing some of my favorites that I use all the time, like del.icio.us. Accordingly, I've put together a page of the activities I use. MSDN has all the info on creating Activities.

Activities are very similar to other existing features in other browsers including the ability to add context menu items to IE. There's two important differences which make activities better. Activities have a preview window that pops out when you hover over an activity, which is useful to get in place information easily provided by developers. The other is that the interface is explicit and takes after HTML FORMs and OpenSearch descriptions. Because the interface is explicitly described in XML (unlike the context menu additions described above which run arbitrary script) we have the ability to use activities in places other than on a webpage in the future. And because activity definitions are similar to HTML FORMs, if your webservice has an HTML FORM describing it you can easily create an activity.